1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method and a program, and more particularly, to an image processing apparatus, an image processing method and a program which performs image conversion for a two-dimensional image to generate a binocular disparity image corresponding to stereopsis.
2. Description of the Related Art
In the related art, a variety of proposals has been made for apparatuses and methods which convert a two-dimensional image into a binocular disparity image corresponding to stereopsis. The binocular disparity image generated on the basis of the two-dimensional image includes a pair of a left eye image, which is observed by the left eye, and a right eye image, which is observed by the right eye. As the binocular disparity image including the pair of the left eye image and the right eye image is displayed through a display apparatus which can separate the binocular disparity image into the left eye image and the right eye image to respectively provide the separated images to the left eye and the right eye of an observer, the observer can perceive the images as a three-dimensional image.
Such an image generation or display process is disclosed in the following related art techniques.
For example, Japanese Unexamined Patent Application Publication No. 9-107562 discloses an image processing configuration for a dynamic image moving horizontally. Specifically, according to this configuration, an original image is output as one of a left eye image and a right eye image, and an image delayed in a field unit is output as the other thereof. Through such an image output control, an object moving in the horizontal direction is perceived as being in front of the background.
Further, Japanese Unexamined Patent Application Publication No. 8-30806 discloses an apparatus in which a left eye image and a right eye image are shifted from each other by a preset amount in the horizontal direction for a still image or an image having a small movement and thus the image is perceived as floated.
Further, Japanese Unexamined Patent Application Publication No. 10-51812 discloses a technique in which an image is divided into a plurality of disparity calculation regions, a pseudo-depth is calculated from a characteristic amount of the image in each region, and a left eye image and a right eye image are horizontally shifted in the opposite directions on the basis of the depth.
Further, Japanese Unexamined Patent Application Publication No. 2000-209614 discloses a technique similar to Japanese Unexamined Patent Application Publication No, 10-51812, which while changing, on the basis of a delay amount calculated from a characteristic amount of an image, the horizontal delay amount of a left eye image and a right eye image, limits the horizontal delay amount to prevent a retinal image difference from occurring any more than is necessary, thereby preventing a degree of fatigue of the eyes.
Further, Japanese Unexamined Patent Application Publication No. 2005-151534 discloses a technique in which characteristic amounts of upper and lower portions of an image are calculated, and the synthesis ratio of a plurality of scene structures indicating preset depth information is adjusted, to thereby express the image as a combination having a simplified structure.
However, the related art techniques as described above have the following problems.
In the image conversion apparatus as disclosed in Japanese Unexamined Patent Application Publication No. 9-107562, preferable stereopsis can be provided for only an object moving at a constant speed in the horizontal direction. In an image including a plurality of moving objects or complex movements, the binocular disparity is not correctly set, and thus the objects are arranged in unnatural positions or the retinal image difference becomes excessively large. Thus, stereopsis may not be formed.
Further, the image conversion apparatus as disclosed in Japanese Unexamined Patent Application Publication No. 8-30806 provides only the shift of the entire screen for the still image or the image having a small movement, but has great difficulty in expressing the anteroposterior relation of the objects in the image.
In the image conversion apparatuses as disclosed in Japanese Unexamined Patent Application Publication Nos. 10-51812 and 2000-209614, the pseudo-depth is estimated from the characteristic amounts of the image, but since the estimation is based on such an assumption that the sharpness, luminance and saturation of the object in the front of the screen are high, the estimation is not necessarily performed in a correct manner. Thus, an incorrect retinal image difference is given to the object having the incorrect depth estimation, thereby resulting in the arrangement in an incorrect position.
The image conversion apparatus as disclosed in Japanese Unexamined Patent Application Publication No. 2005-151534 is configured to allow the structure of the image to be adapted for a simple and limitative structure and suppresses generation of unnatural depth. However, all the related art techniques as described above have the following common problem. That is, a relatively large retinal image difference is generated in the generated binocular disparity image, and the binocular disparity image is three dimensionally displayed using a three-dimensional display apparatus. In general, such a three-dimensional display apparatus is used that the image is observed using special glasses for stereopsis, such as a passive eyeglass-type in which an image is divided through a polarization filter, or a color filter to be observed by the left eye and the right eye or an active eyeglass type in which an image is temporally divided from side to side through a liquid crystal shutter.
When viewing the binocular disparity image having the large retinal image difference, an observer can perceive the stereoscopic effect depending on the retinal image difference with such glasses for stereopsis. However, when viewing the screen without the glasses, the observer comes to view double images in which the left eye image and the right eye image overlap with each other by a large amount and does not view the images as a normal two-dimensional image. That is, the image converted through these related art image conversion apparatuses can be viewed only with the glasses.
Further, the large retinal image difference may affect fatigue of the observer. For example, Japanese Unexamined Patent Application Publication No. 6-194602 discloses that in a case where the left eye image and the right eye image are each shifted by a large amount, a discrepancy occurs between control of the angle of convergence and adjustment of the lens in a view direction in the real world, so that the discrepancy leads to fatigue in stereopsis using the binocular disparity.
Further, in the image conversion apparatuses as disclosed in Japanese Unexamined Patent Application Publication Nos. 10-51812, 2000-209614 and 2005-151534, the pseudo-depth is estimated from the image, but it is difficult to detect a detailed depth from a single image. For example, in the case of minute structures such as branches of trees, electric cables or hairs, the depth estimation is not easy. Thus, it is difficult to obtain the stereoscopic effect for minute objects.